9 research outputs found
In-medium mass from the reaction
Data on the photoproduction of mesons on nuclei have been
re-analyzed in a search for in-medium modifications. The data were taken with
the Crystal Barrel(CB)/TAPS detector system at the ELSA accelerator facility in
Bonn. First results from the analysis of the data set were published by D.
Trnka et al. in Phys. Rev. Lett 94 (2005) 192303 \cite{david}, claiming a
lowering of the mass in the nuclear medium by 14 at normal nuclear
matter density. The extracted line shape was found to be sensitive to
the background subtraction. For this reason a re-analysis of the same data set
has been initiated and a new method has been developed to reduce the background
and to determine the shape and absolute magnitude of the background directly
from the data. Details of the re-analysis and of the background determination
are described. The signal on the target, extracted in the
re-analysis, does not show a deviation from the corresponding line shape on a
target, measured as reference. The earlier claim of an in-medium mass
shift is thus not confirmed. The sensitivity of the line shape to
different in-medium modification scenarios is discussed.Comment: 13 pages and 11 figures, submitted for publicatio
Photoproduction of Neutral Pions off Protons
Photoproduction of neutral pions has been studied with the CBELSA/TAPS
detector in the reaction for photon energies between 0.85
and 2.50 GeV. The mesons are observed in their dominant neutral decay
mode: . For the first time, the differential cross
sections cover the very forward region, . A
partial-wave analysis of these data within the Bonn-Gatchina framework observes
the high-mass resonances (2190), (2080), and (2070).Comment: 12 pages, 9 figures, minor modifications to PWA sectio
Development of Low-Noise / Low-Power Preamplifier for the Readout of Inorganic Scintillators and their Mass Production Test System
On hadron deformation: A model independent extraction of EMR from pion photoproduction data
Photoproduction of η and η' mesons off protons
Total and differential cross sections for eta and eta(`)photoproduction off the proton have been determined with the CBELSA/TAPS detector for photon energies between 0.85 and 2.55 GeV. The eta mesons are detected in their two neutral decay modes, eta -<gamma gamma and eta -< 3 pi(0)-< 6 gamma, and for the first time, cover the full angular range in cos theta(c.m.) of the eta meson. These new eta photoproduction data are consistent with the earlier CB-ELSA results. The eta(`) mesons are observed in their neutral decay to pi(0)pi(0)eta -< 6 gamma and also extend the coverage in angular range
Photoproduction of π<sup>0</sup> η on protons and the Δ (1700)D<sub>33</sub> -resonance
Total and differential cross-sections for the reaction γp → π<sup>0</sup>ηp have been measured with the
Crystal Ball/TAPS detector using the tagged photon facility at the MAMI C accelerator in Mainz. In the
energy range E<sub>γ</sub> = 0.95–1.4 GeV the reaction is dominated by the excitation and sequential decay of the
Δ(1700)D<sub>33</sub>-resonance. Angular distributions measured with high statistics allow us to determine the ratio
of hadronic decay widths Γ<sub>ηΔ</sub>/Γ<sub>πS11</sub> and the ratio of the helicity amplitudes A<sub>3/2</sub>/A<sub>1/2</sub> for this resonance